Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation
Abstract
A laboratory study of cryogenic fracturing was performed to test its ability to improve oil/gas recovery from low-permeability reservoirs. Our aim is to develop well-stimulation technologies using cryogenic fluids [e.g., liquid nitrogen (LN)] to increase permeability in a large reservoir volume surrounding wells. The new technology has the potential to reduce formation damage caused by current stimulation methods and minimize or eliminate water usage. The concept of cryogenic fracturing is that a sharp thermal gradient (thermal shock) created at the surfaces of formation rocks by applying cryogenic fluid can cause strong local tensile stress and start fractures. We created a laboratory system for cryogenic fracturing under true-triaxial loading, with LN-delivery/control and -measurement systems. The loading system simulates confining stresses by independently loading each axis up to approximately 5,000 psi on 888-in. cubes. Temperature in boreholes and at block surfaces and fluid pressure in boreholes were continuously monitored. Acoustic and pressure-decay measurements were obtained before and at various stages of stimulations. Cubic blocks (8 88-in.) of Niobrara shale, concrete, and sandstones were tested, and stress levels and anisotropies varied. Three schemes were considered: Gas fracturing without cryo-stimulation, gas fracturing after low-pressure cryogen flow-through, and gas fracturing after high-pressure cryogen flow-through. Findingsmore »
- Authors:
-
- Texas A & M Univ., College Station, TX (United States)
- King Abdulaziz Univ., Jeddah (Saudi Arabia)
- Colorado School of Mines, Golden, CO (United States)
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Publication Date:
- Research Org.:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Org.:
- USDOE Office of Science (SC)
- OSTI Identifier:
- 1567129
- Grant/Contract Number:
- AC02-05CH11231
- Resource Type:
- Accepted Manuscript
- Journal Name:
- SPE Journal
- Additional Journal Information:
- Journal Volume: 23; Journal Issue: 04; Journal ID: ISSN 1086-055X
- Publisher:
- Society of Petroleum Engineers (SPE)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 42 ENGINEERING; Well stimulation; Cryogenic Fracturing; Unconventional reservoir; Thermal shock; Shale and tight gas reservoirs
Citation Formats
Cha, Minsu, Alqahtani, Naif B., Yao, Bowen, Yin, Xiaolong, Kneafsey, Timothy J., Wang, Lei, Wu, Yu-Shu, and Miskimins, Jennifer L. Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation. United States: N. p., 2018.
Web. doi:10.2118/180071-pa.
Cha, Minsu, Alqahtani, Naif B., Yao, Bowen, Yin, Xiaolong, Kneafsey, Timothy J., Wang, Lei, Wu, Yu-Shu, & Miskimins, Jennifer L. Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation. United States. https://doi.org/10.2118/180071-pa
Cha, Minsu, Alqahtani, Naif B., Yao, Bowen, Yin, Xiaolong, Kneafsey, Timothy J., Wang, Lei, Wu, Yu-Shu, and Miskimins, Jennifer L. Wed .
"Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation". United States. https://doi.org/10.2118/180071-pa. https://www.osti.gov/servlets/purl/1567129.
@article{osti_1567129,
title = {Cryogenic Fracturing of Wellbores Under True Triaxial-Confining Stresses: Experimental Investigation},
author = {Cha, Minsu and Alqahtani, Naif B. and Yao, Bowen and Yin, Xiaolong and Kneafsey, Timothy J. and Wang, Lei and Wu, Yu-Shu and Miskimins, Jennifer L.},
abstractNote = {A laboratory study of cryogenic fracturing was performed to test its ability to improve oil/gas recovery from low-permeability reservoirs. Our aim is to develop well-stimulation technologies using cryogenic fluids [e.g., liquid nitrogen (LN)] to increase permeability in a large reservoir volume surrounding wells. The new technology has the potential to reduce formation damage caused by current stimulation methods and minimize or eliminate water usage. The concept of cryogenic fracturing is that a sharp thermal gradient (thermal shock) created at the surfaces of formation rocks by applying cryogenic fluid can cause strong local tensile stress and start fractures. We created a laboratory system for cryogenic fracturing under true-triaxial loading, with LN-delivery/control and -measurement systems. The loading system simulates confining stresses by independently loading each axis up to approximately 5,000 psi on 888-in. cubes. Temperature in boreholes and at block surfaces and fluid pressure in boreholes were continuously monitored. Acoustic and pressure-decay measurements were obtained before and at various stages of stimulations. Cubic blocks (8 88-in.) of Niobrara shale, concrete, and sandstones were tested, and stress levels and anisotropies varied. Three schemes were considered: Gas fracturing without cryo-stimulation, gas fracturing after low-pressure cryogen flow-through, and gas fracturing after high-pressure cryogen flow-through. Findings from pressure-decay tests show that LN stimulation clearly increases permeability, and repeated stimulations further increase the permeability. Acoustic velocities and amplitudes decreased significantly after cryo-stimulation, indicating fracture creation. In the gas fracturing without the stimulation, breakdown (complete fracturing) occurs suddenly without any initial leaking, and major fracture planes form along the plane containing principal-stress and intermediate-stress directions, as expected theoretically. However, in the gas fracturing after cryogenic stimulations, breakdown occurred gradually and with massive leaking because of thermal fractures created during stimulation. In addition, the major fracture direction does not necessarily follow the plane containing the principal-stress direction, especially at low confining-stress levels. In tests, we observed that cryogenic stimulation seems to disrupt the internal stress field. The increase in borehole temperature after stimulation affects the permeability of the specimen. When a stimulated specimen is still cold, it maintains high permeability because fractures remain open and local thermal tension is maintained near the borehole. When the rock warms back, fractures close and permeability decreases. In these tests, we have not used proppants. Overall, fractures are clearly generated by low- and high-pressure thermal shocks. The added pressure of the high-pressure thermal shocks helps to further propagate cryogenic fractures generated by thermal shock. Breakdown pressure is significantly lowered by LN stimulation, with observed breakdown-pressure reductions up to approximately 40%.},
doi = {10.2118/180071-pa},
journal = {SPE Journal},
number = 04,
volume = 23,
place = {United States},
year = {Wed Aug 01 00:00:00 EDT 2018},
month = {Wed Aug 01 00:00:00 EDT 2018}
}
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Cited by: 26 works
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Figures / Tables:
Figure 1: True triaxial loading device: (a) Containment ring housing the specimen and actuators, (b) Closeup inside the ring showing the axes and the faces of the specimen.
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Works referencing / citing this record:
The Effect of Thermal Shocking with Nitrogen Gas on the Porosities, Permeabilities, and Rock Mechanical Properties of Unconventional Reservoirs
journal, August 2018
- Elwegaa, Khalid; Emadi, Hossein
- Energies, Vol. 11, Issue 8
Figures / Tables found in this record:
Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.